Food ingredient

ABSTRACT

This invention relates to a food ingredient, comprising a heat-set protein gel and a polysaccharide hydrocolloid which is present in an amount sufficient to influence the structure and texture of the gel, and a process for the preparation of the food Ingredient.

[0001] This invention relates to food ingredients, to methods for thepreparation of such food ingredients and to food products comprisingsuch ingredients. The invention is particularly, but not exclusively,concerned with food ingredients for use in reduced-fat foods, and withthe use of dairy whey protein in the preparation of such reduced-fatfoods.

[0002] Whey is the co-product from the manufacture of dairy productswhich utilise the casein proteins of milk. It contains principallylactose, minerals and the whey proteins representing approximately 20%of the total protein of cows' milk. The whey proteins are represented inmajority by the two proteins, α-lactalbumin and β-lactoglobulin. In aprevious invention a process was described for the fractionation ofthese major whey proteins in Australian Patent No. 616,411.

[0003] International Patent Application No. WO93/00832 (PCT/AU92/00331)(the full disclosure of which is hereby incorporated herein) describesgelled food products in which microparticulate suspensions arestabilised in heat-set gels for food applications. When restrictedprotein unfolding occurs as a result of heating certain globularproteins in solution, gelation may occur if specific interactionsbetween protein molecules enable an ordered three-dimensional network tobe formed. Such interactions effect intermolecular cross-linkinginvolving hydrogen bonding, ionic and hydrophobic interactions. Adjunctsto such interacting protein systems which affect some or all of suchcross-linking mechanisms may serve to modify the overall structure,texture and rheological properties of the gelled product.

[0004] Of the milk proteins. only certain of the whey proteins arecapable of heat-induced gelation, β-lactoglobulin is considered to bethe most important whey protein for gelation since it is capable offorming uniform gels of high strength. Application of the whey proteinfractionation technology developed by Pearce, yields a product which ishighly enriched in β-lactoglobulin and referred to as “β-Fraction”. Thisproduct also displays the capability of forming uniform gels of highstrength. (see Pearce, R.J. (1991) Applications of cheese whey proteinfractions. Food Research Quarterly 51; 74-91.)

[0005] Stading and Hermansson have described the structure andappearance of β-lactoglobulin gels over a range of pH values and havedescribed the clear gels formed below pH 4.0 and above about pH 6.5 asfine-stranded gels and the more turbid gels formed at intermediate pH asaggregate gels. The fine stranded gels formed at low pH were brittle butin the higher pH range were rubber-like. (see Stading, M. & Hermansson.A.M. (1991) Large deformation properties of β-lactoglobulin gelstructures. Food Hydrocolloids 5: 339-352.) The ability to form heat-setgels from food proteins is not limited to β-lactoglobulin or to wheyproteins. For example, heat set gelation of egg white protein is wellknown. Variation in the appearance and texture of such egg white gelsmay be achieved by manipulation of the ionic strength and pH as has beendescribed by Hegg, P.O. (1982) Conditions for the formation ofheat-induced gels of some globular food proteins. Journal of FoodScience 47, 1241-1244, in a manner similar to that shown forβ-lactoglobulin by Stading, M and Hermansson, A-M. (1993) Largedeformation properties of β-lactoglobulin gels. Food Hydrocolloids 5,339-352.

[0006] By combining the results. described in International PatentApplication No. WO93/00832 with the results of Stading et al., weidentified novel gelled food products in which the appearance andtexture of the gelled product could be varied from clear to opaque andfrom elastic to inelastic according to the environmental conditions ofthe protein during the heat-gelation process. The resulting productsdemonstrated rheological characteristics of potential value in theformulation of novel foods. However, under textural analysis, theseproducts, whether essentially elastic or inelastic showed distinct yieldpoints (gel breaking points). This property was considered undesirablefor certain food applications.

[0007] We have now found that incorporation of a polysaccharidehydrocolloid into a heat-gelled protein results in a gelled materialhaving a modified structure and texture which, rheologically, does notdisplay a distinct fracture point (gel breaking point). In thisbehaviour, the gelled product exhibits the textural and rheologicalproperties of a fat (exemplified herein by a texture profile of lard,see Graph 13 ) and enables the material to be utilised as a foodingredient, e.g. a texture modifier, in food products, and especially asan ingredient in reduced-fat foods.

[0008] According to one aspect of the present invention, there isprovided a food ingredient, characterised in that it comprises aheat-set protein gel and a polysaccharide hydrocolloid which is presentin an amount sufficient to influence the structure and texture of thegel.

[0009] The heat-set protein gel is formed by heating a suitable gellableprotein. Suitable gellable proteins may be sourced from egg white, bloodserum or whey. The protein is preferably derived from a whey productrich in β-lactoglobulin, most preferably enriched β-lactoglobulin in theform of β-Fraction.

[0010] The preferred polysaccharide hydrocolloid is carrageenan.especially iota- or kappa-carrageenan.

[0011] A food product, in accordance with this invention can consistsolely of the food ingredient defined above. More usually, however, thefood product will contain other ingredients which may be incorporatedinto the protein gel or which may be simply mixed with the gel. Forexample, as described in WO93/00832, an edible food ingredient may bemixed with, or dispersed in, a solution of the gellable protein beforeit is heated to form the gel. Alternatively, the gel may be formed firstand then mixed with the other ingredient(s), some of which are alsodescribed in WO093/00832. Examples of such ingredients include fats oroils (which may be incorporated in a microparticulate state) andparticulate foods such as meats or fruits.

[0012] One application of the food ingredients of the invention(referred to herein as “texture-modified gelled products”) is in thereplacement of fat in products to which fat is normally added. Typicalof such application is the replacement of added fat, such as pork backfat, in manufactured meat products in which the added fat contributesadvantageously to the texture of the food and may be a special featureof its appearance. The texture-modified gelled products may be choppedor minced and used in manufactured meat products in a manner comparableto that currently employed for fat incorporation. For example, areduced-fat Strassburg-type sausage may be manufactured in which thetypical pieces of visible fat are replaced by the texture-modifiedgelled product.

[0013] In another application of the texture-modified gelled products inpreparing reduced-fat food materials, the texture-modified gelledproduct is added as an additional constituent of the finished productthereby effectively reducing the overall fat content of the finishedproduct. For this purpose. the texture-modified gelled product mayincorporate microparticulate oil or fat emulsion to contribute tomouthfeel and the ability to carry fat-soluble colour, flavour ornutritionally advantageous materials. Alternatively. such lipidicmaterial may be omitted if such additional contributions are notrequired. Food applications of this type may be in the form of extendedmanufactured meat products including extended ham and chopped meatproducts. In such applications the texture-modified gelled products mayprovide a desirable texture and mouthfeel and through additionallyincorporated coloured microparticulate material or soluble colourantsmay resemble in appearance the meat constituents. Such extended foodproducts alternatively may be meat analogues or manufactured fish andseafood products.

[0014] A yet further application of the texture-modified gelled productsis in the formation of new or modified foods in which food pieces ofvisible dimensions (i.e. not microparticulate) are incorporated anddistributed through the gelled product. When so used, thetexture-modified gelled product provides a base material of desirabletexture which may be augmented by incorporation of insolublemicroparticulates and soluble materials to enhance the colour, flavourand nutritional value or inclusion of larger food material pieces forspecial appearance or texture. This type of product may incorporate amicroparticulate emulsion and pieces of food material of meat, fish.egg, vegetable or other origin.

[0015] According to another aspect. the invention provides a process forthe preparation of a food ingredient as defined above. which comprisesthe steps of:

[0016] (i) preparing a solution of gellable protein at a concentrationsuch that when mixed with other components of the formulation a uniformgel will be formed on being heated;

[0017] (ii) if necessary, adjusting the pH of the protein solution to bein the range 3.5 to 7.5;

[0018] (iii) preparing a solution of an appropriate polysaccharidehydrocolloid at a concentration such that. when mixed with the solutionof gellable protein from (i) and other components of the formulation, itwill result in a fat-like texture in the resulting heat-gelled proteinproduct;

[0019] (iv) heating the polysaccharide hydrocolloid solution to activatethe hydrocolloid and subsequently holding at a temperature in the range50° to 60° C. to maintain solubility;

[0020] (v) heating the protein solution from (i) to a temperature in therange 50° to 60° C. as selected in (iv);

[0021] (vi) mixing the heated solutions from (iv) and (vi) inproportions such that the gellable protein content of the mixture is inthe range 5 to 15% and the polysaccharide hydrocolloid concentration isin the range 0 to 1%;

[0022] (vii) if necessary, adjusting the pH of the mixture from (vi) tobe in the range 3.5 to 7.5, as selected in (ii);

[0023] (viii) heat treating the mixture from (vi) or (vii) at atemperature and for a time sufficient to form a gelled product; and

[0024] (ix) cooling the heat-gelled product to ambient or sub-ambienttemperature.

[0025] If desired. an emulsion of an edible fat or oil heated to atemperature in the range 50° to 60° C. as selected in (iv) and, ifnecessary. having its pH adjusted to the value selected in (ii), can beadded to the mixture at step (vi).

[0026] Water-soluble substances, such as colorants, flavorants andsweeteners may be added, if required, to the solution at an appropriatestep, e.g. (i) or (ii).

[0027] Lipid-soluble colorants, flavorants and other adjuncts such asnutritionally advantageous materials may be included in the lipidicphase of any emulsion added at step (vi).

[0028] One or more insoluble microparticulate materials, which maycontribute to colour, flavour or nutritive value may be incorporatedinto the texture-modified gelled product, by adding them, if necessarvin the form of a dispersion at an appropriate step of the process.

[0029] Insoluble materials of microparticulate or visible dimensions mayalso be included in the composite mixture prior to heat gelation.

[0030] Generally. activation of the hydrocolloid should be carried outin accordance with the manufacturer's specifications.

[0031] The preferred parameters for the composition of the product andfor the process of its preparation are now described in more detail.

[0032] The rigidity of the gelled product prepared by heating a solutionof a protein containing a polysaccharide hydrocolloid under controlledconditions is determined primarily by the concentration of protein. Forβ-Fraction, generally, the lower limit of concentration is 5%. whichtypically represents the minimum concentration of protein for gelformation and the upper limit is 15%, which typically represents themaximum usable hardness of a gel for use in a food system. The preferredconcentration of β-Fraction for a fat-like product is in the range 8 to12%.

[0033] We have discovered that a number of polysaccharide hydrocolloidsaffect the structure and texture of whey protein/β-Fraction gels; sucheffects include increased granularity and increased or reducedwater-holding ability of the heat-set protein gel. For the preparationof fat-like products for use as ingredients in reduced-fat foods, anumber of polysaccharides have been evaluated. The incorporation ofcarrageenan is preferred. While effects on the structure and texture ofheat-set, β-Fraction gelled products have been observed afterincorporation of carrageenan at all levels in the range 0 to 1%, at lowlevels of incorporation (less than 0.15%) a gel strengthening effect wasobserved. At higher levels, further structural and textural effects ofthe added carrageenan were observed such that, while the gelled productremained firm and cohesive, no distinct fracture point was discernible.The preferred concentration of carrageenan in the gelled product is inthe range 0.2 to 0.4%.

[0034] The nature of the gelled product, and particularly its texture,is also determined by the pH. Generally the pH will be in the range 3.5to 7.5. For the gelled products comprising β-Fraction and carrageenanonly to have fat-like properties, the preferred pH is in the range 5.8to 6.8, more preferably 5.9 to 6.2. At the lower end of this last range,i.e. pH 5.9-6.1 the gelled products will have a soft texture. A firmerproduct is obtained at about pH 6.2.

[0035] The heat gelation process occurs at a temperature in excess ofthe denaturation temperature of β-actoglobulin which is in the range 71to 75° C. dependent on pH and other environmental parameters. The gelledproduct may be prepared by heating at a temperature in the range 65 to100° C. The gel firmness increases with the time of heating up to amaximum value. Generally. the heating time will be in the range 5 to 120minutes. For comparative analytical purposes, the preferred heatingconditions may be stated as: immersion of the sample, tightly containedin a 50mm diameter water-impermeable casing, in a water-bath at 90° C.for 30 minutes followed by cooling in running cold water.

[0036] As indicated above, the β-Fraction and polysaccharidehydrocolloid gelled product may optionally contain an emulsion of fat oroil. While apparently contributing little to the structure and textureof the gelled product, incorporation of some lipidic material assiststhe mouthfeel of the product. Up to 20% by weight of the lipidicmaterial may be present, the preferred level of addition being such thatthe concentration of lipidic material in the final product is in therange 5 to 10%. The emulsion may conveniently be prepared by emulsifyingan edible fat or oil by homogenisation with sufficient protein ornon-protein emulsifier in aqueous dispersion at a temperature in therange 50° to 60° C. as selected in step (iv) above to form a stableoil-in-water emulsion and. if necessary. adjusting the pH to be in therange 3.5 to 7.5, as selected for step (ii).

[0037] The invention is further described and illustrated by referenceto the following non-limiting examples.

EXAMPLE 1

[0038] This example shows that the texture of the gelled product isaltered by the incorporation of polysaccharide hydrocolloid as evidencedby the amount of free serum, the yield point and maximum firmnesstogether with the rupture profile.

[0039] (i) Gelled product with no suspended microparticulates

[0040] Two aqueous solutions of β-Fraction (89%protein on a dry matterbasis; 83% of the protein being β-lactoglobulin) were prepared at pH6.10 and a protein content of 9%(w/w) and warmed to 60° C. 2.5%solutions of carrageenan were prepared from iota-carrageenan (ViscarinME389 Tech. spec. 448) and kappa-carrageenan (Gelcarin ME911 Tech. spec.481), both manufactured by FMC Corporation, Marine Colloids Division,1735 Market Street, Philadelphia Pa. 19103, USA. For activation of thecarrageenans in accordance with the manufacturers instructions, thesolutions were heated to 85° C. then cooled to 60° C. Compositesolutions were made by combining different weights of carrageenansolution and β-Fraction solution to give final carrageenanconcentrations in the range 0 to 0.3%. A control sample was preparedwithout carrageenan.

[0041] Aliquots (120 ml) of each solution were placed and sealed inGlowrap PVDC seamless casing of 50mm flat width. Each sample was heatedby immersion in a water bath at 90° C. for 30 min., cooled in runningtap-water for 1 hour, refrigerated for 15 min. and equilibrated at 20°C. Slices 30 mm in length were cut from the gelled protein product andevaluated for gel strength i.e. yield point, fracture point and maximumfirmness using a Stable Micro Systems TAXT2 texture analyser incompression mode with a test speed of 0.8 mm/sec and fitted with a flat10 mm diameter circular disc probe which was applied to the centre ofthe cut surface. A pre-weighed piece of adsorbent paper was placed undereach sample during rupture testing. After completion of each test. thesample was removed , the paper reweighed and the weight difference notedas a measure of the expelled free moisture/fat. Results are shown inTables 1.1 and 1.2 for iota-carrageenan and kappa-carrageenanrespectively. Reported values are each the mean of three determinations.TABLE 1.1 Iota-carrageenan Yield Compression Carrageenan point′ MaximumFree at yield Graph conc. % w/w (kg) firmness (kg) moisture/fat point(%) number 0.00 0.384 0.457 0.097 34.38 1 0.10 0.431 0.431 0.057 25.61 20.30 0.203 0.238 0.076 20.06 3

[0042] TABLE 1.2 Kappa-carrageenan Yield Compression Carrageenan point′Maximum Free at yield Graph conc. % w/w (kg) firmness (kg) moisture/fatpoint (%) number 0.00 0.384 0.457 0.097 34.38 1 0.10 0.140 0.172 0.20620.35 4 0.3 0.108 0.123 0.132 19.50 5

[0043] (ii) Gelled product containing suspended microparticulates

[0044] A microparticulate dispersion of lard in water was prepared at60° C. by 4-stage homogenisation using an homogeniser ex Milko-Tester MkII (Foss Electric) using β-Fraction to stabilise the emulsion at anoil:protein ratio of 45:2. The microparticulate dispersion at 60° C wasmixed with solution of β-Fraction and carrageenan solution if requiredas in Example 1(i) to give a final concentration of 9%(w/w) of proteinand a final fat content of 7.5%(w/w).

[0045] Aliquots of each mixture were heated to stabilise themicroparticulate dispersion in a gelled protein-carrageenan matrix orgelled protein only matrix, as in the control, under conditions as inExample 1(i). Results are shown in Tables 2.1 and 2.2 for iota- andkappa-carrageenans respectively. Each of the values reported is a meanof three determinations. TABLE 2.1 Iota-carrageenan Yield CompressionCarrageenan point′ Maximum Free at yield Graph conc. % w/w (kg) firmness(kg) moisture/fat point (%) number 0.00 0.139 0.175 0.161 19.15 6 0.050.499 0.499 0.064 22.77 7 0.10 0.432 0.432 0.065 15.93 8 0.30 0.2710.381 0.056 14.73 9

[0046] TABLE 2.2 Kappa-carrageenan Yield Compression Carrageenan point′Maximum Free at yield Graph conc. % w/w (kg) firmness (kg) moisture/fatpoint (%) number 0.00 0.139 0.175 0.161 19.15 6 0.05 0.339 0.339 0.10816.67 10 0.10 0.392 0.392 0.182 18.11 11 0.3 0.209 0.280 0.122 11.72 12

[0047] Yield point is taken as the value of firmness at the point ofdeviation from linearity in the Firmness versus Distance plot shown inthe accompanying graphs generated by the Stable Micro Systems TAXT2texture analyser. For comparison purposes Graph 13 shows the performanceof a sample of lard tested under the same conditions as the othersamples.

EXAMPLE 2

[0048] This example shows that certain other whey products rich inβ-lactoglobulin display similar ability to form heat-set gels which canalso be texture modified by inclusion of polysaccharide hydrocolloidsuch as carrageenan.

[0049] Two aqueous solutions of a whey protein concentrate derived fromacid casein whey (75.9% protein on a dry matter basis; 71% of theprotein being β-lactoglobulin) were prepared at pH 6.10 and a proteincontent of 9%w/w. lota-carrageenan was added to one of the solutions butnot the other. Gelled products were prepared as in Example 1(i). Sampleswere evaluated for textural properties as in Example 1(i). Results areshown in Graph 14.

EXAMPLE 3

[0050] This example shows that protein other than whey protein displayssimilar ability to form heat-set gels which can also be texture modifiedby inclusion of polysaccharide hydrocolloid such as carrageenan.

[0051] Two aqueous solutions of spray dried egg white (85.3% protein ona dry matter basis) were prepared at pH 6.10 and a protein content of9%w/w. Iota-carrageenan was added to one of the solutions but not theother. Gelled products were prepared as in Example 1(i).

[0052] Samples were evaluated for textural properties as in Example1(i). Results are shown in Graph 15.

[0053] Throughout this specification and any claims which follow, unlessthe context requires otherwise, the word “comprise”, or variations suchas “comprises” or “comprising”, will be understood to imply theinclusion of a stated integer or group of integers but not the exclusionof any other integer or group of integers.

[0054] Those skilled in the art will appreciate that the inventiondescribed herein is susceptible to variations and modifications otherthan those specifically described. It is to be understood that theinvention includes all such variations and modifications which fallwithin its spirit and scope. The invention also includes all the steps.features. compositions and compounds referred to or indicated in thisspecification. individually or collectively. and any and allcombinations of any two or more of said steps or features.

The claims defining the invention are as follows:
 1. A food ingredient,characterised in that it comprises (a) a heat-set protein gel which isformed by heating a gellable milk protein rich in β-lactoglobulin; and(b) a polysaccharide hydrocolloid which is present in an amountsufficient to influence the structure and texture of the gel.
 2. A foodingredient as claimed in claim 1, characterised in that the gellableprotein is derived from a whey product.
 3. A food ingredient as claimedin claim 2, characterised in that the gellable protein is enrichedβ-lactoglobulin in the form of β-Fraction.
 4. A food product,characterised in that it comprises the food ingredient of any one ofclaims 1 to
 3. 5. A food product as claimed in claim 4, characterised inthat it includes a microparticulate oil or fat emulsion.
 6. A foodproduct as claimed in claim 4 or claim 5, characterised in that itincludes food pieces of visible dimensions.
 7. A food product as claimedin any of claims 4 to 6, characterised in that it includes one or moreadditional water-soluble or lipid soluble substances.
 8. A process forthe preparation of a food ingredient as defined in any one of claims 1to 3, characterised in that it comprises the steps of: (i) preparing asolution of the gellable protein at a concentration such that when mixedwith other components of the formulation a uniform gel will be formed onbeing heated; (ii) if necessary, adjusting the pH of the proteinsolution to be in the range 3.5 to 7.5; (iii) preparing a solution of anappropriate polysaccharide hydrocolloid at a concentration such that,when mixed with the solution of gellable protein from (i) and othercomponents of the formulation, it will result in a fat-like texture inthe resulting heat-gelled protein product; (iv) heating thepolysaccharide hydrocolloid solution to activate the hydrocolloid andsubsequently holding at a temperature in the range 50° to 60° C. tomaintain solubility; (v) heating the protein solution from (i) to atemperature in the range 50° to 60° C. as selected in (iv); (vi) mixingthe heated solutions from (iv) and (v) in proportions such that thegellable protein content of the mixture is in the range 5 to 15% and thepolysaccharide hydrocolloid concentration is up to 1%; (vii) ifnecessary, adjusting the pH of the mixture from (vi) to be in the range3.5 to 7.5, as selected in (ii); (viii) heat treating the mixture from(vi) or (vii) at a temperature and for a time sufficient to form agelled product; and (ix) cooling the heat-gelled product to ambient orsub-ambient temperature.
 9. A process as claimed in claim 8,characterised in that an emulsion of an edible fat or oil heated to atemperature in the range 50° to 60° C. as selected in (iv) and, ifnecessary, having its pH adjusted to the value selected in (ii), isadded to the mixture at step (vi).
 10. A process as claimed in claim 9,characterised in that, a lipid soluble material is added to the edibleoil or fat.
 11. A process as claimed in any one of claims 8 to 10,characterised in that an additional water-soluble substance is added tothe protein solution or the hydrocolloid solution.
 12. A process forproducing a food product characterised in that the process claimed inany one of claims 8 to 11 is carried out, with the addition of one ormore microparticulate insoluble materials, which may contribute tocolour, flavour or nutritive value and/or the addition of insoluble foodmaterials of visible dimensions for incorporation into the gelledproduct, at an appropriate step.